A summary of traditional electrostatic microactuator design techniques is given by Legtenberg, Groeneveld and Elwenspoek in their paper “Comb-drive actuators for large displacements”, J. Micromech. Microeng., 1996. Unfortunately, the features described therein do not have adequate side-stiffness for increased deflection.
Miniature devices, such as micromechanical or micromachined devices, having movable members supported above a substrate by one or more suspension members have been disclosed. See, for example, U.S. Pat. No. 5,998,906 which discloses a linear microactuator for translating a mirror in and out of a beam of light in an optical disk drive system. The suspension members disclosed therein have a constant width along the length thereof.
The use of notched flexures for high precision macroscopic mechanisms is known. Such flexures often consist of a pair of semi-circular notches removed from a relatively thick beam such that the beam appears to rotate about a pivot point approximately at the center of the notches. See, for example, “Parallel spring stages with flexures of micrometric cross-section” by Henin, Bottinelli and Clavel, SPIE Vol. 3202, 1998, pp 209-219. Unfortunately, notched flexures are quite stiff due to the limited amount of material subject to bending in the notch region. Additionally, since all of the strain in the flexure is localized, the maximum angular deflection of such a flexure is limited by the maximum strain which the material can tolerate without failure. As a result, these flexures are typically used in small deflection instrumentation applications where substantial actuation force is available from electromagnetic or piezoelectric actuators. The difficulty in maintaining the required width tolerance of the hinge during the fabrication of these devices has additionally made them expensive to manufacture and limited their use.
The use of bossed diaphragms is known in the design and fabrication of piezoresistive pressure sensors. See in this regard “Piezoresistive silicon sensor for very low pressures based on the concept of stress concentration” by Hein, Schlichting, and Obermeier, Technical Digest of the 7th International conference on Solid-State Sensors and Actuators, Yokomaha, June, 1993, pp 628-631. The goal of such diaphragms, however, is to enhance the measuring of small pressure differences.
In general, it is an object of the present invention to provide a miniature device having a suspension member for supporting a movable member over a substrate.
Another object of the invention is to provide a miniature device of the above character in which the suspension has a high compliance in the desired direction of motion.
Another object of the invention is to provide a miniature device of the above character in which the suspension member has a high side stiffness.
Another object of the invention is to provide a miniature device of the above character in which the suspension member has a minimal device area.
Another object of the invention is to provide a miniature device of the above character capable of translating an optical element.